As is well know, a pressure sensor measures pressure, such as air pressure or liquid pressure, and generates a signal as a function of the pressure imposed. Pressure sensors are used for control and monitoring in thousands of everyday applications, such as, for example, home appliances, air conditioners, medical devices, aerospace, general industry, and automotive vehicles. In automotive vehicles, for example, pressure sensors can be included in the anti-theft system to detect a broken window, in the crash module to predict the severity of an impact and the need for airbag deployment, in tires to determine whether tire pressure is dangerously low, in the engine compartment to achieve optimal engine conditions, in the emission control system to help protect the environment from noxious emissions from the fuel tank, and other areas.
FIGS. 1A and 1B depict a conventional pressure sensor assembly 100 placed in existing automotive vehicles for detecting a side impact. The pressure sensor (not shown) included within the assembly 100 detects a side impact if the change in pressure between ambient conditions and crash conditions exceeds a predetermined threshold. Upon detecting an impact, the pressure sensor sends a signal to the Restraint Crash Module (RCM) to deploy the airbags. To ensure timely and effective deployment, the pressure sensor can be designed to have a short response time from impact detection to airbag deployment, such as, for example, six to ten milliseconds (ms).
As shown in FIG. 1A, the pressure sensor assembly 100 includes a housing 102 for the pressure sensor and a nozzle 104 coupled to the housing 102. The nozzle 104 includes an open end 106 for permitting airflow into the housing 102 and to the pressure sensor. A predetermined minimum amount of airflow is required through the nozzle in order to produce effective pressure changes that can be measured by the pressure sensor. FIG. 1B shows a cross-sectional view of the pressure sensor assembly 100 along the indicated axis. A printed circuit board (PCB) 108 is disposed within the housing 102 below the nozzle 104. The assembly 100 can further include a small port (not shown) between the nozzle 104 and the PCB 108 for allowing airflow from the nozzle 104 to the PCB 108. The dimensions of the nozzle 104 and the small port can be specifically configured to produce the minimum air flow rate required for operation of the pressure sensor.
Incidentally, certain types of ants, such as, for example, raspberry crazy ants (also known as tawny crazy ants), are especially attracted to electrical equipment, including that found in automotive vehicles, air conditioning units, home appliances, and the like. Moreover, ants appear to be particularly attracted to the pressure sensors included in such electrical equipment for a number of possible reasons. For starters, the ants may be attracted by the opening and/or geometry of the pressure sensor nozzle and the airflow therethrough because it appears to resemble ant tunnels and paths in natural ground. For example, a typical nozzle opening may be about eight millimeters by six millimeters (mm), which provides ample space for the passage of small ants, such as the raspberry crazy ants that are typically 1.5-2.0 mm wide. In addition, ants may be attracted to the silicon gel material placed inside pressure sensors for insulation. For example, the silicon gel is typically placed over a heat source, such as the sensing electronic circuit (e.g., the PCB 108), and the temperature of this sensing circuitry appears to be close to the ants comfort zone temperature.
Once inside the pressure sensor, the ants may use the silicon gel for nesting and consumption and in the process, can become electrocuted. Accumulation of dead ants and nest debris within the pressure sensor can damage the electronic circuitry by, for example, causing short circuits, wire corrosion, overheating, and/or related mechanical failures. In vehicle crash modules, such damage can cause a disruption in communication between the pressure sensor and the RCM, which can lead to certain anomalies. Further, the presence of ants within the pressure sensor, including the nozzle and the small port inside the housing, can interrupt the airflow rate required for pressure sensor performance.